\(\left|2x+1\right|=7\)
Xét trường hợp 1:
\(2x+1=7\)
\(\Leftrightarrow2x=7-1\)
\(\Leftrightarrow2x=6\)
\(\Leftrightarrow x=6:2\)
\(\Leftrightarrow x=3\)
Xét trường hợp 2:
\(2x+1=-7\)
\(\Leftrightarrow2x=-7-1\)
\(\Leftrightarrow2x=-\left(7+1\right)\)
\(\Leftrightarrow2x=-8\)
\(\Leftrightarrow x=-8:2\)
\(\Leftrightarrow x=-4\)
Vậy x=3 hoặc x=-4
\(\left|2x+1\right|=7\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+1=7\\2x+1=-7\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=8\\2x=-6\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-3\end{matrix}\right.\)
Vậy...
